The most common words that day were 'war', 'evil', 'sympathy', 'solidarity', 'determination' and, of course, 'change'. Above all, it was accepted that the world had changed. How could it be otherwise?

The reason for such a description was also not hard to divine. The first attempt to attack the World Trade Center, in 1993, had been foiled, but the planning this time had obviously been meticulous. The enemy had been prepared to wait until it had acc.u.mulated the necessary means and opportunity.

However, more than that, a terror attack of this scale was not calculated to do limited damage. It was designed for maximum casualty. It was delivered by a suicide mission. It therefore had an intent, a purpose and a scope beyond anything we had encountered before. This was terror without limit; without mercy; without regard to human life, because it was motivated by a cause higher than any human cause. It was inspired by a belief in G.o.d; a perverted belief, a delusional and demonic belief, to be sure, but nonetheless so inspired.

It was, in a very real sense, a declaration of war. It was calculated to draw us into conflict. Up to then, the activities of this type of extremism had been growing. It was increasingly a.s.sociated with disputes that seemed unconnected, though gradually the connection was being made. Kashmir, Chechnya, Algeria, Yemen, Palestine, Lebanon; in each area, different causes were at play, with different origins, but the attacks, carried out as acts of terror, were growing, and the ideological link with an extreme element that professed belief in Islam was ever more frequently expressed. Until September 11, the splashes of colour on different parts of the canvas did not appear to the eye as a single picture. After it, the clarity was plain, vivid and defining.

We look back now, almost a decade later when we are still at war, still struggling and managing the ghastly consequences which war imposes, and we can scarcely recall how we ever came to be in this position. But on that bright New York morning, not a cloud disturbing the bluest of blue skies, we knew exactly what was happening and why.

We knew that so far as we were concerned we had not provoked such an outrage. There had been acts of terror committed against us: Lockerbie, the USS Cole Cole, the US emba.s.sy in Tanzania. We had tried to retaliate, but at a relatively low level. They were individual tragedies, but they did not amount to a war. They were the price America paid for being America. The other conflicts we reckoned were none of our business; or at least they were the business of our diplomatic corps, but not of our people.

So those carrying out such acts were wicked; but they weren't changing our world view. George Bush had won the presidency after the controversies of the most contested ballot in US history, but the battle between him and Al Gore had focused mainly on domestic policy. At my first meeting with him Camp David in February of the same year his priorities were about education, welfare and cutting down on big government as he saw it.

So there was no build-up to September 11, no escalation, no attempts to defuse that failed, no expectation or inevitability. There was just an attack planned obviously during the previous presidency of unbelievable ferocity and effect. No warning, no demands, no negotiation. Nothing except ma.s.s slaughter of the innocent.

We were at war. We could not ignore it. But how should we deal with it? And who was this enemy? A person? A group? A movement? A state?

I was in Brighton that day, to give the biennial address to the Trades Union Congress. Frankly, it was always a pretty ghastly affair for both of us. As I explain elsewhere, I was frustrated they wouldn't modernise; they were frustrated with my telling them how to do their business. Not that they were ever slow in telling me how to do mine, mind you. And sure-fire election-losing advice it was too. They ignored my counsel; and I ignored theirs. For all that, we sort of rubbed along after a fashion, and in a manner of speaking, and up to a point.

The great thing about Brighton is that it is warm, closer than Blackpool to London, and retains the enormous charm of yesteryear. Blackpool can be a great town and has a unique quality, but it needs work done on it. Brighton was where Neil Kinnock did a photocall on the pebble beach on the day he became Labour leader in 1983, lost his footing and fell in the sea. You can imagine the pleasure of the a.s.sembled press. It must have been replayed a thousand times and became a slightly defining misstep; unfairly so, of course; but such things are never fair. In public, you are always on show, so always be under control. The trick, actually, is to appear to be natural, while gripping your nature in a vice of care and caution. Don't let the mask slip; don't think this is the moment to begin a new adventure in communication; don't betray excesses of emotion of any kind; do it all with the ease and character of someone talking to old friends while knowing they are, in fact, new acquaintances.

Over time, I began to think there was never a moment when I could be completely candid and exposed. You worried that even sitting in your living room or in the bath, someone would come to photograph, question and call upon you to justify yourself. I became unhealthily focused on how others saw me, until, again over time, I refocused on how I saw myself. I realised I was public property, but the freehold was with myself. I learned not to let the opinion of others, even a prevailing one, define my view of myself and what I should or should not do.

The TUC took place in early to mid-September, and the party conference a couple of weeks later. Both always made September a little nerve-tingling. From the TUC you could get a sense of where the party were liable to be in terms of contentment and/or otherwise. Trouble at the first usually presaged trouble at the second. The 2001 TUC was no exception. Having just won our first ever consecutive full term, in a second landslide victory, you would have thought it an occasion for general rejoicing. 'I think mostly they'll want to congratulate you on the victory,' Alastair said to me, po-faced, as we boarded the train.

'Do you think so?' I said, perking up.

'Don't be ridiculous,' he replied.

Sure enough, the mood as I arrived at lunchtime was the usual mixture of sweet and sour, but with the sweet a decided minority. I went straight to the Grand Hotel. We had an hour and a half before I had to go to the new Conference Centre a hundred yards or so along the beachfront. I worked in the bedroom as the team gathered in the living room of the suite. Just after a quarter to two, around 8.45 Eastern Standard Time, Alastair was called out of the room by G.o.dric Smith, his very capable deputy. Alastair came back in, turned on the television and said, 'You'd better see this.' He knew I hated being interrupted just before a speech, so I realised I'd better look. The TV was showing pictures of the Trade Center like someone had punched a huge hole in it, fire and smoke belching forth. Just over fifteen minutes later, a second plane hit, this time graphically captured live on-screen. This was not an accident. It was an attack.

At that moment, I felt eerily calm despite being naturally horrified at the devastation, and aware this was not an ordinary event but a world-changing one. At one level it was a shock, a seemingly senseless act of evil. At another level, it made sense of developments I had seen growing in the world these past years isolated acts of terrorism, disputes marked by the same elements of extremism, and a growing strain of religious ideology that was always threatening to erupt, and now had.

Within a very short s.p.a.ce of time, it was clear the casualties would be measured in thousands. I ordered my thoughts. It was the worst terrorist attack in human history. It was not America alone who was the target, but all of us who shared the same values. We had to stand together. We had to understand the scale of the challenge and rise to meet it. We could not give up until it was done. Unchecked and unchallenged, this could threaten our way of life to its fundamentals. There was no other course; no other option; no alternative path. It was war. It had to be fought and won. But it was a war unlike any other. This was not a battle for territory, not a battle between states; it was a battle for and about the ideas and values that would shape the twenty-first century.

All this came to me in those forty minutes between the first attack and my standing up in front of the audience to tell them that I would not deliver my speech but instead return immediately to London. And it came with total clarity. Essentially, it stayed with that clarity and stays still, in the same way, as clear now as it was then.

Immediately I saw that, though it was a war, because of its nature it would have to be described and fought differently. It was, in a profound sense, a battle that was ideological, the mores and modus vivendi of religious fanaticism versus those of an enlightened, secular system of government that in the West, at least, incorporated belief in liberty, equality and democracy. It was also a battle about modernisation, a clash not so much between civilisations, but rather one about the force and consequence of globalisation.

All around the globe, the new technology the Internet, computers, mobile phones, ma.s.s travel and communication was opening the world up, casting people together, mixing cultures, races, faiths in a vast melting pot of human interaction. With this, came the reaction. In the West, it often took the form of virulent nationalism, waves of anti-immigrant feeling as people saw their traditional ident.i.ty being weakened and their control over the world around them being surrendered, economically and culturally.

Within Islam, other, deeper forces were at work. Many distrusted globalisation, worried about the way it changed society, worried about ceding authority to it. Many disliked Western culture, its brash insistence on liberal att.i.tudes, its s.e.xual freedom, its individualism that could and sometimes did lapse into hedonism. All of this would have produced its own reaction. But what deepened it and turned it into a powerful radicalising potency was peculiar to Islam. For centuries, Islam had not only been a dominant religious movement in the Middle East and beyond, but had also achieved political dominance and led the world in science, art and culture.

For hundreds of years after the death of Christ, as Christianity was spread first by those scorned and persecuted by the Roman Empire and then as the official religion of the Empire, it became the accepted or enforced religion of countries that today we know as Muslim: Egypt, Palestine, Lebanon, Syria, Iraq. There are still pockets of Christians in each today, though less than there were; and they descend from Christian communities that pre-date Islam.

By the seventh century, Christianity was riven by division, schisms and battles over what was heresy and what wasn't. Once martyred and persecuted, the Christians then hounded not only those who weren't Christian, but also those Christians who disagreed with the orthodoxy. For a religion based on compa.s.sion and love, it was a dismal picture.

When Islam began, and within the s.p.a.ce of twenty or so years was established by the Prophet Muhammad into the government of what we now know as Saudi Arabia and beyond, it was in part an attempt to take the Abrahamic faiths back to their roots and develop them into a principled, rational and moral way forward for the world. The message of the Prophet was given to him by the angel Gabriel from G.o.d the Koran therefore being the direct recital of the word of G.o.d.

At least to begin with, Islam was a welcome contrast with the state of Christianity. Where Christian armies would routinely butcher their foes, Islam showed mercy. Where other religions were forcibly suppressed, Islam showed tolerance. Where priests and prelates often lived lives of debauchery and vice, the followers of Islam seemed genuine disciples of devotion and discipline to G.o.d.

As Islam expanded far beyond Mecca and Medina, it was often looked upon as a liberator, even by some of the Christian communities such as the Nestorians in Iraq. In time, of course, as it became more powerful it also became more dictatorial. Non-believers were offered a choice conversion or taxation and the price of the latter became uncomfortably high. Nonetheless, there is a fair case for saying that up to and through the Crusades, and until around the European Renaissance, Islam was the greater repository of civilised thought.

The history of Islam its origins, its rise, its present predicament is essential to understanding the significance of the events of September 11. It is precisely here that I made a mistake: I misunderstood the depth of the challenge. I was ignorant of the pervasive nature of the phenomenon. As at September 11 2001, I accepted what most accepted: this act was perpetrated by a small group of fanatics wholly unrepresentative of Islam who could and should be crushed.

If I had known then that a decade later we would still be fighting in Afghanistan, I would have been profoundly perturbed and alarmed.

I hope I would have still taken the same decision, both there and in respect of Iraq. To have tried to escape the confrontation would have been a terrible error, an act of political cowardice. What I know now does not make me any less committed to the fight we began on the day of the event itself. On the contrary, it is even more clear to me that the battle has to be fought with every means at our disposal, and fought until it is won.

What is clear now is the scale of the challenge, which in two senses is different to what we originally contemplated. The first is that in the mindset that is modern Islam, there is one spectrum, not several. At the furthest end of the spectrum are the extremists who advocate terrorism to further their goal of an Islamic state, a rebirth of the caliphate that came into being in the years following the death of the Prophet. It is true they are few in number, but their sympathisers reach far further along the spectrum than we think. While many do not agree with the terrorism, they 'understand' why it is happening.

Still further along the spectrum are those who condemn the terrorists, but in a curious and dangerous way buy into bits of their world view. They agree with the extremists that the US is anti-Islam; they see the invasion of Afghanistan or Iraq as invasions of Muslim nations because they were Muslim nations. They see Israel as the symbol of Western anti-Islamic prejudice. This group stretches uncomfortably far into the middle of the spectrum.

Then you have, of course, a large number, probably the majority, who condemn the terrorists and their world view.

But and here is the second point even this group have not yet confidently found their way to articulating a thoroughly reformed and modernising view of Islam. In other words, it is true they find the terrorism repugnant and they wish to be in alliance with the Western nations against it, but this does not yet translate into an alternative narrative for Islam that makes sense of its history and provides a coherent vision for its future. What this means is that very often countries in the Arab and Muslim world will offer their people a disconcerting and ultimately self-defeating choice between a ruling elite with the right idea, but which they are reluctant or fearful to advertise, and a popular movement with the wrong one, which they are all too keen to proclaim.

The combination of all of this means that this battle is not, I'm afraid, one between a small, unrepresentative group of extremists and the rest of us. Or at least, it is not only that. It is also a fundamental struggle for the mind, heart and soul of Islam.

In that struggle we are necessary partic.i.p.ants, both because we came under attack and also because those who must lead Islam to change need our support. In the final a.n.a.lysis, of course, it is a struggle that must be won from within. Such struggles don't last an electoral cycle; they last a generation.

Back in the instant following the cataclysmic act of terrorism that stunned, shocked and appalled the world, the issue was clear: the madmen had declared war. They would be rooted out and eliminated. No one doubted it. No one or very few disputed it, or the action that followed.

Be under no illusion whatever and the period since then is littered with illusions there were only two ways of dealing with this phenomenon. One was to manage it; to have left the Taliban in power but ringed them with sanctions and alliances; to have adopted a purely soft-power approach to the challenge. Some indeed advocated this strategy (though not many did so on 12 September), and I do not dismiss it. It is the true alternative to what we actually did. The idea would have been to have worked for gradual reform and the appearance of a new Islam over time. So we would have been provoked to war; and resisted the provocation.

The other way, the way we chose, was to confront it militarily. I still believe that was the right choice, but the costs, implications and consequences were far greater than any of us, and certainly me, could have grasped on that day.

To win in this way would not and does not require simply a military strategy to defeat an enemy that is fighting us. It requires a whole new geopolitical framework. It requires nation-building. It requires a myriad of interventions deep into the affairs of other nations. It requires above all a willingness to see the battle as existential and to see it through, to take the time, to spend the treasure, to shed the blood, believing that not to do so is only to postpone the day of reckoning, when the expenditure of time, treasure and blood will be so much greater. Who knows which is right? No one. We will only know later. Just as our knowledge was limited on September 11 2001, so our knowledge remains limited now. In such circ.u.mstances, in such conditions of understanding, the only course is to follow instinct and belief. There is nothing more to do. That is what I did in those days following the tragedy.

All these years on and still fighting, people look at the situation and ask: What went wrong? This ignores the possibility that it is not so much a case of 'what went wrong', as that the nature of the struggle means that it will turn and twist and evolve over a long time. We thought back then that the equation was relatively simple: knock out the Taliban, give Afghanistan a UN-supervised election, provide billions for development, and surely the outcome is progress. And, of course, without an enemy using terror to disrupt and destabilise, without the tribal and warlord factions of a failed state, if the people had been allowed to do what they wanted, they would indeed have decided for progress. In fact, in so far as they could, they did, and at every election came out and showed what they wanted and what they didn't. But even with our support, even with the activity of our forces and the aid we give, the people's will for order has not yet been able to overcome the countervailing will for chaos.

However, the conclusion from this is not that we give up; still less that if we had never bothered, we or the people would be better off. The conclusion is that the war is brutal and long. And that is exactly what makes it all the more important to win.

The paradigm through which we see all this today is that we cannot see the end in sight and meanwhile we are losing brave and committed soldiers in a fight whose outcome is uncertain. But in any serious war, such an issue is at some point reached and the question then is whether to retreat or to press forward. The soldiers are not being killed because the cause is any less just and not necessarily because it is being badly prosecuted; they are being lost because the enemy is fighting us; because for them, too, the stakes are high and because they can see the possibility, if they last out, that we will lose heart or cobble together some ignominious deal in which we will trade the essential principles we are fighting for, in return for calm. Then they will re-emerge stronger, and their ideology with them.

So it is important to recall why the war in Afghanistan happened. It did so because on that fateful day, terrorists harboured by the Taliban and trained in Afghanistan showed that they would kill innocent people on a hitherto unknown scale, to drive us out of alliance with those in Islam who want peaceful coexistence and force us to leave that world to the ideology of religious extremism, to government by fanatic or dictator. We did not seek them out. They sought us. Had it not been September 11, it would have been another occasion.

In the immediate aftermath, too, we were unsure of where the next strike might come. For some time afterward, we had an emergency procedure in place if a plane was over London or any major city and had lost contact with air traffic control. Basically there was a series of escalations of alarm up to the point where I could be asked to authorise bringing the plane down. Fighters were on standby ready to go up in the air and shoot it out of the sky if so ordered. It only happened once. I recall it, as you can imagine, vividly. I was at Chequers at the weekend and was called urgently to the phone. A pa.s.senger plane had been out of contact for some time, and was heading over London. I had the senior RAF commander authorised to get my decision. The fighter jet was airborne. For several anxious minutes we talked, trying desperately to get an instinct as to whether this was threat or mishap. The deadline came. I decided we should hold back. Moments later the plane regained contact. It had been a technical error. I needed to sit down and thank G.o.d after that one!

As I left the stage of the TUC ironically given a better reception than any I ever enjoyed I was already putting in train the emergency meetings that would take the proximate decisions for Britain's security. I also fixed calls with the key world leaders, including of course President Bush. I took calls from the main ministers and the Cabinet Secretary on the train back to London.

It was a strange journey as we sat in the carriage riding through the peaceful and beautiful Suss.e.x countryside, such a contrast to the fevered concentration of the conversations about a world whose security had just been turned upside down. At that point, though, as I have said, I was relatively calm, clear in my own mind about what had to be done.

Back in Downing Street and during the first of several emergency sessions with ministers and officials, we ran through the measures we had to take. Flights over London were suspended, the police and security services were put on red alert. The intelligence people were dispatched to ferret out any possible plots here. Every part of Whitehall was buzzing and alive with activity. At such moments the machine is at its best, covering all bases, setting an agenda for the decision-making, joining up the disparate parts in some sort of semi-automatic cohesion. It was impressive. I was glad of the steady hand of Richard Wilson and his senior Civil Service colleagues.

I spoke in turn to Putin, Schroeder, Chirac and Berlusconi, and the next day to President Bush. The collective sense of solidarity was absolute. Everyone was fully behind the US. It is hard now to realise just how fearful people were at that time. For all we knew, there were other attacks about to happen. At any moment, we expected to hear of some fresh atrocity.

I saw my role as that of galvanising the maximum level of support. I knew that when the immediate impact of the event diminished, there was always a danger of backsliding; and I also knew the key thing was to a.s.semble as broad a coalition of support for action as possible. On the night of September 11, I set out our position as a country in a broadcast from Downing Street: This ma.s.s terrorism is the new evil in our world. The people who perpetrate it have no regard whatever for the sanct.i.ty or value of human life, and we the democracies of the world must come together to defeat it and eradicate it. This is not a battle between the United States of America and terrorism, but between the free and democratic world and terrorism. We, therefore, here in Britain stand shoulder to shoulder with our American friends in this hour of tragedy, and we, like them, will not rest until this evil is driven from our world.

'Shoulder to shoulder' came to be something of a defining phrase. I chose the words carefully. I was aware this was a big commitment that would come to be measured not in words but in actions; and I knew the road on which we were going to travel 'shoulder to shoulder' was going to be rocky. How rocky, as I say, I did not know, but I think and hope that had I known, my words would have been the same.

I took this view for reasons both of principle and of national interest (and, incidentally, have never believed the two are mutually exclusive). As a matter of principle, I was sure that we should see the atrocity as an attack not on the US per se, but because the US was the leader of the free world, it was therefore an attack on us too. It was also in our national interest to defeat this menace and if we wanted to play a major part in shaping the conduct of any war, we had to be there at the outset with a clear and unequivocal demonstration of support. I believed in the alliance with America, I thought its maintenance and enhancement a core objective of British policy, and I knew that alliances are only truly fashioned at times of challenge, not in times of comfort.

Over the next days, I rallied support. I hosted Silvio Berlusconi who, as ever, was straightforward in his commitment to the US. I visited France and Germany and they too were on board, though I noticed with a little anxiety that Jacques Chirac particularly was urging caution in respect of any response. Parliament was recalled and I made a statement. Opinion was universally among Opposition leaders at least supportive.

On 20 September, I travelled to the US. By then, my position as the world leader strongly articulating the need for comprehensive and strategic action was pretty well established. My concern throughout was to make sure America felt embraced and supported, felt a real arm of solidarity stretched out towards them. The fear, but above all the sense of anger and outrage, would be enormous. How it was channelled would be a product not just of how America's leaders spoke to their own people, but of how the outside world expressed its sympathy and also its readiness to share responsibility.

Of course, the other crucial point was that many Britons had lost their lives. I met families of those who had died. Such encounters are always the hardest thing you do. You have to retain the dignity of office but you genuinely feel the grief, and can often not help expressing it in tears. One woman I met was pregnant. Her husband had flown over for a meeting in the World Trade Center. He and his child would never see one another. Other parents mourned the loss of their only son, whom they plainly idolised. I was shocked by the hideous random nature of terrorism. Dead just because you happened to be there. No other reason. No other explanation. Just the merest happenstance.

Having landed in New York, we went to St Thomas Church on Fifth Avenue. The mayor Rudy Giuliani was there. I liked him instantly. He was under immense pressure but he seemed to be not only coping, but stepping forward and giving a strong sense of leadership. I had a message from the Queen that was to be read out, and then gave a short reading myself. The Queen's message was strong and clear. The words I quoted were from Thornton Wilder's novel The Bridge of San Luis Rey The Bridge of San Luis Rey about five people who die when a bridge collapses over a gorge: about five people who die when a bridge collapses over a gorge: But soon we die, and all memory of those five will have left Earth, and we ourselves shall be loved for a while and forgotten. But the love will have been enough. All those impulses of love return to the love that made them. Even memory is not necessary for love. There is a land of the living and a land of the dead and the bridge is love, the only survival, the only meaning.

As we stepped outside the church, a battery of cameras and journalists a.s.sailed us and I spoke some words which I had thought about on the ride from the airport: I can only imagine what it must have been like for the people of New York for the past nine days . . . My father's generation went through the Blitz. They know what it is like to suffer this deep tragedy and attack. There was one country and one people which stood by us at that time. That country was America and those people were the American people. As you stood by us in those days, we stand side by side with you now. Your loss is our loss. Your struggle is our struggle.

I felt Rudy next to me relax and take comfort as I spoke. I could see on the faces of people we walked past an intense, earnest desire to know if they had friends at this moment of trial; if America was alone or with others; if the world meant the words spoken and would follow through with deeds. I wanted to a.s.sure them that this was so, that at least Britain would not be wanting, that what we said we meant, that we would be at the front and not the back.

We finally got to Washington, an hour late for the meeting with President Bush, who was to address both Houses of Congress that night. As I drove up to the back entrance of the White House, the one I used on so many occasions, where the immaculately dressed marines stood to attention either side of the door, I wondered how I would find George. We had spoken on the phone a few times. We had already started to exchange ideas. After the initial shock, he had handled himself exceptionally well, and plainly had the American people right behind him.

I went into the Oval Office. He was there putting the finishing touches to the speech. It had been agreed I would sit in the gallery to hear it, side by side with George's wife Laura. He was unbelievably, almost preternaturally calm. We even had dinner together. I reflected that faced with a similar speech, I would have been closeted away, drafting and redrafting. I would have been dismayed at having to entertain someone. I offered to slip away but emphatically he said no, stay, let's talk, and we did until it was time for him to go over. I suddenly realised two things about him (and at that time I did not know him nearly as well as I came to): the first was that he sincerely welcomed the friendship I and Britain had showed. He didn't just appreciate it; he found it a source of strength. Second, he was not panicking or fretting or even plain worrying. He was at peace with himself. He had his mission as president. He hadn't asked for it. He hadn't expected it. He hadn't found it. It had found him. But he was clear. The world had changed, and as president of the world's most powerful country, he was tasked with making sense of that change and dealing with it.

As we got into the lift, he as ever exchanging a bit of banter with the lovely George Hannie, the maitre d' of the White House flat, I asked him if he was nervous. 'No, not really,' he replied. 'I have a speech here and the message is clear.' I marvelled at it, looked carefully at him; but yes, he did indeed appear completely at ease.

It was the first time I had seen a speech to Congress. (In 2003 I would deliver one myself.) It was an extraordinary affair, something that only the US could do with that elan and confidence. As the president spoke, you could feel the representatives come together around love of the nation, the pride, patriotism and self-belief exuding from every pore of that wonderful arena of mahogany, bra.s.s and stone, rich in history, certain of the future. George singled me out in the gallery alongside Laura and I duly took a bow, somewhat self-consciously.

As I looked down on the a.s.sembled ranks, so forthright, so determined, so sure, I reflected on what lay ahead. I a.s.sumed we could dislodge the Taliban. I had already worked out that it should be done by a tactical manoeuvre of offering them a choice: yield up bin Laden and the terrorists, or be removed from power. And then what? I knew little about Afghanistan, but I did know it was a country that over the centuries had been invaded, occupied and plundered yet always seemed eventually to swallow and spit out the invaders.

Some months before, sitting in the Long Gallery in Chequers surrounded by the portraits of the previous tenants and Cromwell memorabilia, including his swords at the Battle of Naseby, I had stumbled upon a three-volume set of diaries. They were by Field Marshal Roberts, an officer and then head of the British Army in the mid- to late nineteenth century, including the time of the Indian Mutiny. They were fascinating reading, and gave a brilliant first-hand account of what it was like to be a young officer, recounting the events of the mutiny, how it spread and how it was put down, conveying a vivid sense of that part of the British Empire. They described battles in Hyderabad and Peshawar and then in the Hindu Kush, in Kandahar, Helmand and Lashkar Gah, names all too familiar today.

They also showed the remarkable spirit of the British soldier. As the mutiny took hold and it all arose out of the false rumour that native Muslim soldiers in the British Army had had their rifles greased with pork the British troops were pushed back and towns were overrun. The native soldiers, well trained and well equipped by the very people they now set out to kill, fought fiercely. For a time, things hung in the balance. Nawabs, the princes of India, calculated which way it would go, some joining the mutiny, others giving provender to the rulers.

Roberts gave one incredible account of how, as they prepared to storm a redoubt of the mutiny, there was a fierce argument among the soldiers, as to who should have the honour of going first into the breach that the artillery would make in the city wall. To go first was certain death. But the compet.i.tion to do it was, for all that, intense. Eventually, to their great delight, the argument was won by Scots Highlanders. Duly they went in first; duly they died. But how the pride of their regiment swelled at the endeavour.

In these diaries, Afghanistan was regarded differently: more bleak, more savage, more ungovernable. As the Russians discovered a hundred years later, the country had its own way.

So I had committed us; but I did so knowing that war is unpredictable, and in Afghanistan especially so. Partly as a result of this, I thought it essential that the battle we were about to embark upon was not simply a war to punish. It had to liberate. Yes, the cause was the attack on the Twin Towers, but once the engagement began, it couldn't just be a retaliation, a reprisal, a redress of a wrong done to us. It had to be of bigger reach, intent and purport. Precisely because this struggle was connected with an ideology that was not confined to Afghanistan indeed had been imported into Afghanistan the ambition had to be greater. All this would add to the weight of it and the responsibility to see it through.

Overnight on 20 September we flew into Brussels for an emergency European Council the next day. I had deliberately decided to go to the US before the Council met, so that when I arrived I could speak directly of what I had seen and experienced in New York and Washington. Europe had stayed very strongly behind the US, but now when we came to the point of action, you could never be sure. In the event the Council went well, and came out with a satisfactory statement unifying people in condemnation and recognising the need for action. The memory of the events was still uppermost in the minds of politicians and public alike; the news was more or less given over to it and would remain so for several weeks as more details emerged, the human stories of tragedy, sacrifice, suffering and heroism became clear, and the implications were a.n.a.lysed and sunk in.

Those implications were vast. If the terrorists could have killed more, they would have. If instead of 3,000 it had been 30,000, they would have rejoiced. For world leaders wondering and worrying where the next hostility would come from, the contemplation not only of what had happened but what might happen was continuous, urgent and nerve-racking.

In those initial days, even before the war began, and long before Iraq was on the agenda, certain thoughts crystallised and became decisions. One I have described: that this could not be a battle fought on the ideological low ground; it had to be fought on the high ground our values versus theirs. The goal was not simply to remove the Taliban but to replace them with democracy, to rebuild the country. This was not just a matter of idealism, it was also about understanding why Afghanistan had become a failed state, why it had become a breeding ground for terror, why it had descended into this horrible, cruel mix of anarchy and despotism. Like it or not, from then on, we were in the business of nation-building.

Second, the prospect of any such group, or a state which sympathised with them or shared a similar outlook, obtaining nuclear, chemical or biological weapons the so-called WMD trinity was unthinkable. If they got hold of them, there could be little doubt on the evidence of September 11 that they would use them. Indeed, in the days following the attack, anthrax was sent to top Congress, White House and other officials, and the news was full of alarm at the possibility of some form of chemical attack. It was obvious to me that our att.i.tude towards the trade, transfer and development of such weapons had to be of a wholly different kind. A new signal had to be sent out, a new urgency established in order to make it clear that such a possibility const.i.tuted a direct threat to our society.

This was immediately plain, not least out in the Middle East. The issue of Saddam and his ten-year obstruction of weapons inspection was not upfront, but from then on, it was there in the background. There was no decision at that point as to how to deal with him; nevertheless, that he had to be confronted, brought into line or removed was, on any deeper a.n.a.lysis, fairly obvious.

Third, how could such an attack have been planned, developed, supervised and executed without a hint of anyone knowing? If such a plot could be hatched in the USA, where else could similar plots be taking place? From this point on, it seemed to me that the balance in civil liberties between protecting the rights of the suspect and protecting the rights of the citizen had changed. Of course care had to be exercised, and as a lawyer I was only too well aware of the risks of jeopardising our way of life in the name of safeguarding it; but once September 11 had demonstrated this terrorism's capacity and intent, governments round the world especially those closely allied to the US saw the need to take new measures of security and perhaps a new approach to it.

All of these decisions taken certainly with contemporaneous support and understanding were to have far-reaching consequences for the future of both the country and the government. We felt we had been attacked. But more than that: we felt we had been warned.

As I got back to Chequers late on Friday 21 September, I was tired yet also galvanised. If I could have seen into the future, I would also have been deeply disturbed.

The next weeks were spent in a frantic but essentially well-organised process to put together the military operation to remove the Taliban, and the reconstruction plan for Afghanistan.

Despite the pressure, George was determined not to rush 'I don't want a $10 million missile hitting a $10 tent just for effect,' he remarked memorably. He agreed to an ultimatum to the Taliban, so that people could see we had offered a way out if they chose to take it. But it was clear they wouldn't take it.

I was writing regular notes to him, raising issues, prompting his system and mine: humanitarian aid; political alliances, including in particular how we co-opted the Northern Alliance (the anti-Taliban coalition) without giving the leadership of the country over to them; economic development; reconciliation in the aftermath of a hopefully successful military operation. Above all, I was globetrotting to the Middle East, Pakistan, Russia trying to ensure that we kept the support we had. I wrote a personal, private note to my own staff and senior officials, setting out how we needed to get all parts of the system, ours and the Americans', better coordinated.

The UN under Kofi Annan's guidance was being helpful and from the outset I was determined that they should help take the strain of the politics. Fortunately, in Lakhdar Brahimi they had a sensible interlocutor with the Afghans, one who was experienced and savvy.

The meetings abroad went well too. I visited President Putin. At this point, we remained strong allies. He and I sat in a small anteroom in the Kremlin. I always thought how difficult it was to position Moscow culturally. St Petersburg was clearly European, but Moscow was to itself, unplaceable in a broader context, even unfathomable, but impressive in a somewhat intimidating way.

Putin was anxious to help. Through Chechnya he knew the influence of this extremism. He saw a common link between all these different arenas of struggle. Back then, also, he saw the possibility of Russian renaissance and a resurgence of Russian power as compatible with, or even furthered by, being allied to the US. It was one of my regrets that we never got together a proper strategy for allowing him to fulfil that ambition with us, as opposed to what eventually happened, which was an attempt to fulfil it in contradistinction to us. Maybe that was always a fond hope. He and George got on well personally, but Vladimir thought the Americans treated him and Russia with insufficient respect or consequence, and as time wore on he decided to pitch Russia to the international community as the country willing to stand up to America. In Iraq, he found an issue upon which such a role could be played, and he played it with his customary vigour. We should have made greater efforts; in particular, the Americans tended to underestimate him, and that was never a good idea.

Nonetheless, in late 2001, we sat and conspired on what we could do to ensure that the former Soviet satellite countries ringing Afghanistan would be supportive or compliant in respect of any action to come. At one moment, he even suggested we fly together that night to Tajikistan to lobby its president personally, a notion I adored, but which my travelling staff quailed at.

President Musharraf of Pakistan was in a difficult position: his government had worked with the Taliban government; the borders between Afghanistan and Pakistan were porous; the tribal and political links were strong, yet he was an ally of ourselves and the US, of course.

On 5 October, we flew in on an RAF plane equipped with special anti-missile devices. I had thought it somewhat of an overreaction, until the moment we began our descent into the airfield. The plane circled sharply, spiralling down in a careful manoeuvre, and as we landed and the rubber squeaked on the tarmac, the crew burst into applause. They were plainly relieved. As we drove in from the airport to Islamabad, I saw roads and streets shut down, but lined nonetheless with large crowds standing up on the embankments, the men in white robes, the women usually veiled, staring, with neither enmity nor friendship obvious.

I was ushered into Musharraf's study in the Presidential Palace. All through the meeting a bodyguard hovered near the door, coming in and standing over us each time the servants brought in tea or refreshments. Musharraf himself was clear in his condemnation of the Taliban and in his offer of help and support. He knew the attack had changed everything. He told me something I reflected upon a good deal in later years: in the 1970s General Zia had made the fatal error of linking Pakistani nationalism to devout Islam, in the course of which he had adopted the manner of a religious as well as a political and military leader, proudly showing the mark on his forehead from being pressed to the ground in prayer. The connection between the two, Musharraf explained, had furthered radicalism in the country, heightened the issue of Kashmir and made reconciliation with India harder.

'Surely,' I said, 'economic development is the key challenge for Pakistan.'

'Of course,' he said, 'but the reality is today Pakistani politics is about nuclear weapons and Kashmir.'

'What can we do to help?' I asked, expecting an answer to do with aid or India.

'Do Palestine,' he immediately shot back. 'That would help.'

I came away pleased with his support, but uneasy at how clearly he felt the ultimate success of the mission was in the balance.

On all these visits I had the full inner team with me. I also had the enormous benefit of Sir David Manning, who had become my chief foreign affairs adviser and who had been in the US at the time of the September 11 attacks. I had by this time already beefed up the centre of Downing Street and I now had the redoubtable Stephen Wall as the European adviser. They were both examples of the best types of mandarin. David was cool, calm, very good under pressure, and creative too, always ready with a strategy to resolve an impa.s.se. Over these months, he was a t.i.tan in the team, truly invaluable. Stephen was very professional and proficient, of course; but underneath you could tell he was a riot of strong emotions, opinions and insights which he longed to have you seize upon and implement. Some you could, some you couldn't. But grey, he wasn't; and I liked that.

Meanwhile, on 7 October the military campaign started. It was largely a bombing campaign, with limited boots on the ground. The Northern Alliance were also advancing. We had identified four core objectives: deny al-Qaeda its Afghan base; deny them an alternative base outside Afghanistan; attack them internationally; support other states in their efforts against them.

From the first attacks in October 2001, the UK was involved alongside coalition forces led by the US under Operation Enduring Freedom (OEF). Royal Navy submarines fired Tomahawk missiles against the Taliban and al-Qaeda networks, and RAF aircraft provided reconnaissance and air-to-air refuelling capabilities in support of US strike aircraft. The US flew missions from Diego Garcia, part of the British Indian Ocean Territory, under permission from the UK government.

UK troops were first deployed in November 2001, when Royal Marines from 40 Commando helped to secure the airfield at Bagram. A 1,700-strong battle group based around 45 Commando was subsequently deployed as Task Force JACANA. Their role was to deny and destroy terrorist infrastructure and interdict the movement of al-Qaeda in eastern Afghanistan. In several major operations, Task Force JACANA destroyed a number of bunkers and caves, and it also provided humanitarian a.s.sistance in areas previously dominated by the Taliban and al-Qaeda. It withdrew in July 2002.

The International Security a.s.sistance Force (ISAF), which aimed to a.s.sist the Afghan Transitional Authority in creating and maintaining a safe and secure environment in Kabul and its surrounding area, was created in December 2001 in negotiations led by the British, authorised by United Nations Security Council Resolution (UNSCR) 1386 and successive resolutions (the latest of which is UNSCR 1776 of 2007). Major General John McColl led the first ISAF mission with contributions from sixteen nations. As well as providing the headquarters and much of the supporting forces for the ISAF, the UK contributed the brigade headquarters and an infantry battalion. Our contribution initially peaked at 2,100 troops, later decreasing to around 300 personnel after the transfer of ISAF leadership to Turkey in the summer of 2002.

The Taliban had collapsed by the end of 2001, remnants melting back into the Pushtun populace in southern Afghanistan and the Pakistani tribal areas. It was important to ensure that Afghanistan did not return to ungoverned s.p.a.ce within which terrorist training and preparation could flourish. International forces therefore remained to provide security and stability, to combat residual Taliban and al-Qaeda elements, and to support the development of Afghan security forces.

At that time, the coalition was still intact, the weight of opinion with us, the objectives clear. In view of what happened subsequently, it is worth stating what the goal was. The a.n.a.lysis we had was that Afghanistan had been a failed state; the Taliban had taken over; and as a consequence extremism under their protection was allowed to grow. An additional destabilising factor was the drugs trade. Afghanistan had become the source of 90 per cent of the heroin that found its way on to the streets of Europe.

Now, years later people say: But the mission isn't clear, or it's confused. It isn't, and it wasn't. To us then, and I believe this to be true now, there is no neat distinction between a campaign to exorcise al-Qaeda, or to prevent Taliban re-emergence, or to build democracy, or to ensure there is a proper, not a narco, economy. There is no 'or' about it. Allow the Taliban to re-emerge, fail to build governance, and you will have the same failed state with the same consequences. The problem is not that we have tried to do too much; it is that to do it requires a complete and sustained engagement, backed by the resources and the will over a very long period.

Up to and through 2004, while the huge scale of the challenge was clear, things nevertheless seemed slowly to be working. I will come later to the decisions of 2006, by which time it was clear that progress had stalled, but from 22 December 2001 when the interim government was installed, through to the 2004 presidential elections when turnout was 70 per cent and large numbers of women voted, through even to the provincial elections in autumn of 2005, Afghanistan seemed to be basically on the path to being a better state, despite the constant diversions, excursions and setbacks aplenty.